The perimeter of a rectangle is 20 feet. of all possible dimensions, the maximum area is 25 square feet when its length and width are both 5 feet. are there dimensions that yield a minimum area? explain.

You will get a very small area if you increase the length  until it is just short of 10 feet
But when it is 10 feet you no longer have a rectangle! Just a straight line with area zero! So there is no real minimum area.

So there is no real minimum value

Okay so for every triangle has three angles that always add up to 180 degrees. and to tell the difference between whether they are secure, right or obtuse is that acute: has one angle that is less than 90 degrees. right triangle means there is at least one angle that is exactly 90 degrees. and an obtuse angle has an angle that is bigger than 180 degrees. i’ll do #13 as an example: 13. 40 and 50 so if every triangle has 180 degrees 40+50= 90 degrees then180-90= 90 degrees so the third angle is 90 degrees and because this triangle has a 90 degree angle it means it is a right triangle